Brushless DC electric motor

ABSTRACT

According to the present invention, a brushless DC electric motor comprising a magnetic rotor, stator and housing. The magnetic rotor comprising a disk installed perpendicular to a shaft and having circumferentially arrayed magnetic poles. The stator comprising at least one circuit board parallel to said disk and said circuit board serves as part of said housing and having circumferentially arrayed coil windings for producing electromagnetic fields.  
     The coil windings being aligned in a radial direction around said shaft to at least partially axially align with said magnetic poles of said disk for providing electromagnetic interaction between said magnetic poles and said coil windings to cause rotation of said magnetic rotor.

FIELD OF THE INVENTION

[0001] The invention is related to electric engineering, and in particular electromagnetic machines, and may be used in the manufacture of electric drives for various purposes, e.g. ventilation, compressors, pumps, wheels of electrically driven automobiles etc.

BACKGROUND OF THE INVENTION

[0002] Well-known are machines of end-face rotor-stator interaction type, where the rotor is a disk, on the end surfaces whereof permanent magnets of alternating polarity are located over the circumference. The stator of such machines is made in the shape of a disk (ring), installed coaxially with the rotor, electromagnetic stator coils being located at the end faces of the stator. For instance, the direct current brushless electric motor (electric drive) described in U.S. Pat. No. 5,440,185, IPC 6H02K 21/12 belongs to this type of electric machines. The known device includes at least one rotor installed on the shaft and made as a multi-pole magnetic disk consisting of sections spaced along the circumference, where the polarity of the sections alternates. The device also includes at least one disk-shaped stator element, determining the rotor position, the device for mounting the rotor (rotors) and stator element (elements) on the common axle, the sensor for positioning the multi-pole magnetic disk versus the stator element and a device to identify the magnetic field profile in the stator elements. Two windings are wound over the stator elements, electric current being fed to one of those thus determining the polarity of the stator poles. The known device is not easy in manufacturing, the biggest difficulty being manufacturing of disk-shaped rotors with magnetic poles of alternating polarity.

[0003] It is known electric drive, the rotor whereof is made of two disks mounted on a shaft with poles distributed over the outer circumference and a cylindrical magnet located between the disks and magnetized in the axial direction, in such a manner that the poles of each disk are the like ones, and in regard to the poles of the other disk—the unlike ones, the stator being made of coils distributed over the circumference, while in accordance with the invention the rotor poles are formed by the teeth located over the outer circumference of both disks in planes perpendicular to the axis of the device, and the poles of the stator coils are arranged in such a way as to allow for their end-face interaction with the rotor poles, the rotor of the device being the subject of the U.S. application Ser. No. 09/621,104 of the same Assignee has no claw-shaped pole horns (poles). The rotor poles are formed by the teeth located over the outer circumference of both disks, which function as magnetic circuits. This ensures streamlined manufacturing of the rotor and its structural strength. The rotor poles are located over the outer circumference of both disks in planes perpendicular to the axis of the device, and the poles of the stator are arranged in such a way as to allow for their end-face interaction with the rotor poles, there arises an opportunity to make the radial size of the device smaller the stator poles may be located in the space between the above-mentioned rotor poles outfitted on both disks. This will make it possible to raise the power of the drive, as the magnetic field in the space between the rotor poles will have the highest intensity. Prior art motor-fans combinations occupy a large space because of the two separate components, the motor and impeller. The present invention utilizes two stator circuit boards in conjunction with a magnetized impeller that requires less space. This new design should result in a more simplified construction and assembly process and yield a reduction in production costs.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide a new brushless DC electric motor and integrated brushless DC electric motor/blower or motor/pump combination as two possible configurations of this design. This electric motor in combination with an impeller for blowers or pumps is capable of significantly reducing an overall height thereof.

[0005] To realize this object, the motor of the present invention is comprised of: a stator comprising circuit board or boards, rotor or rotor/impeller, housing and a controlling device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIGS. 1A, 1B is a plan view of the coils on one side of a stator board and a transparent plan view of the coils on the other side respectively;

[0007]FIGS. 2A, 2B is a sectional view of the coils on stator board 1A and 1B respectively;

[0008]FIG. 3 is a sectional view of the motor;

[0009]FIG. 4 is a sectional viewpoint A of the motor illustrated in FIG. 3;

[0010]FIG. 5 is a sectional view of the motor illustrated in FIG. 3 with ferrous metal plates added;

[0011]FIG. 6 is viewpoint C of the motor illustrated in FIG. 5;

[0012]FIG. 7 is a sectional view of another version of the motor illustrate in FIG. 3 having a single stator board;

[0013]FIG. 8 is a sectional view of an integrated motor/blower;

[0014]FIG. 9 is a sectional viewpoint A of the integrated motor/blower illustrated in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The following is a description of a new brushless DC electric motor design using printed circuit boards for stator coils. We will refer to these printed circuit boards hereafter as stator boards or circuit boards throughout this description. The magnetic rotor is made of a permanent magnet material and may be a monolithic part or an assembly having like magnetic poles. This monolithic part or assembly will be referred to hereafter as a rotor disk or rotor/impeller. The following brief description is broken into six parts: Stator Board, Rotor, Motor Description, Integrated Motor/Blower, Motor Controller and Operation Description.

[0016] Stator Board

[0017] This described stator board is constructed for use with an H-Bridge Drive controller. FIG. 1A illustrates a front side of stator board 1 that contains coils 2 etched from metal, usually copper, on a circuit board substrate 3 and located around the circumference of the stator board. FIG. 1B illustrates a back (transparent) side of the stator board 1 that contains coils 2 a etched from metal, usually copper, on a circuit board substrate 3 and located around the circumference of the stator board. In FIG. 1A one of the coils windings 10 is interrupted (broken) for providing power leads 11 and 12 to the controlling device 13. The two leads from each of the stator boards can be connected parallel or series to one another.

[0018]FIG. 2A illustrates a section of the front side and FIG. 2B illustrates a section of the backside (transparent) of the stator board 1 on FIGS. 1A and 1B respectively. Two layers of coils 2 and 2 a are formed on each side of the stator board. Each of these layers comprises several pairs of coils and each pair made as a spiral. In FIG. 2a the spiral extends from the center 5 of the start coil 6 to the center 9 of the end coil 8 with the same turn direction of the spiral in relation to the both centers 5 and 9. Both layers of coils 2 and 2 a are the same in the transparent view and shifted angularly in such a way that the center 5 of the start coil from one side of the board is electrically connected through circuit board by internal via's 7, which are copper plated holes, with the center 5 a of the other side of the board. Coil 6 a is connected in the same fashion as coil 6 on the front side of the stator board. All coils 2 and 2 a around the stator board are interconnected in this fashion creating a continuous series of coils. These coils can be nickel gold plated which allows the permanent magnets on the rotor to align with them for proper motor startups (Nickel is ferromagnetic at temperatures below 627 degrees Kelvin).

[0019] Rotor

[0020] The rotor 5, illustrated in FIG. 3, can be made from a magnetic plastic material or some other permanent magnet material or a non-magnetic material with permanent magnets 12 imbedded in or attached to it. It is comprised of a disk 5 mounted parallel to stator boards 13 and perpendicular to the axis of rotation 7. It is centrally located between the stator boards and separated from them by a gap 9, 10. Even numbers of magnets 12 are affixed to and distributed around the circumference, preferable outer circumference of disk 5, with equal spacing between each adjacent magnet. The magnetic poles 2, 3 of all individual magnets 12 are aligned in the axial direction and have the same magnetic polarity on one side of the rotor disk.

[0021]FIG. 4 illustrates a sectional viewpoint A of the motor in FIG. 3. The outline of every other coil 4 on a circuit board 13 aligns directly with each magnet 12 on disk 5. Every adjacent pole on one side of the disk has the same magnetic polarity.

[0022] The uni-polar rotor 5 has a maximum number of magnetized disk poles equal to half the number of stator coils 4 on one stator circuit board 13 as illustrated in FIG. 4.

[0023] This rotor disc pole configuration allows for the maximum magnetic interaction between the rotor 5 and stator 13.

[0024] Motor Description

[0025]FIG. 3 illustrates a brushless DC electric motor comprising a magnetic rotor 5, stator 13 and housing 11. The magnetic rotor is comprised of a rotor disk 5 installed perpendicular to its rotating shaft 7 and having circumferentially arrayed magnetic poles 2 and 3. The magnetic poles 2 and 3 on each side of rotor disk 5 have opposite magnetic polarities.

[0026] The stator is comprised of two parallel circuit boards 13 each having circumferentially arrayed coil windings 1 and 4. Each of the coil windings on the two circuit boards share a common axis 15 that is parallel to shaft 7. The opposing stator coil windings, on the two circuit boards, have opposite magnetic polarities with respect to one another.

[0027]FIG. 4 illustrates a sectional viewpoint A of the motor in FIG. 3. The coil windings 4 are aligned in a radial direction around the shaft 7 and at least partially align in a radial direction with the rotor disk magnets 11. This alignment allows for magnetic interaction between the rotor poles 2, 3 and the stator coil windings 1, 4 respectively.

[0028] In FIG. 3, the motor housing 11 also comprises stator boards 13 and bearing supports 14. The motor housing 11 maintains alignment between rotor disk 5 and stator boards 13 and provides for attachment of bearing supports 14. Bearing supports 14 holds bearings 6 allowing rotor disk 5 and shaft 7 to rotate freely. Rotor disk 5 maintains alignment between the stator circuit boards by means of spacers 8.

[0029]FIG. 5 is another version of the motor illustrated in FIG. 3. The exact same motor is used with the addition of ferrous metal plates 16 attached solidly to shaft 7 outside each stator circuit board 13. Plates 16 with radial teeth 17 rotate in unison with rotor disk 5 shortening and thereby concentrating the magnetic flux paths of the rotor poles 2 and 3 through the coil windings 1 and 4 respectively to each adjacent disk tooth 17. This results in a more efficient motor design.

[0030]FIG. 6 illustrates viewpoint C of the motor illustrated in FIG. 5. The coil windings 1 are aligned in a radial direction around the shaft 7 and at least partially aligned in a radial direction with plate teeth 17. This alignment allows for magnetic interaction between the rotor disc poles 2, 3 and the stator coil windings 1, 4 respectively.

[0031]FIG. 7 is a sectional view of a single stator board version of the motor illustrate in FIG. 3. This motor design has only one stator board 13; otherwise it is the same as the motor described in FIG. 3.

[0032] Integrated Motor/Blower

[0033] The unique construction of this motor design makes it very suitable to function as a motor/blower combination. The rotor/impeller will serve as both the motor rotor and blower impeller for moving fluids. This integrated motor/blower operates the same as the motor described in FIG. 3 with the following exceptions:

[0034] 1. The rotor is fashioned into the shape of an impeller based on the particular application required for the device. (Examples might include cross flow fans, centrifugal blowers, or liquid pumps that include sealless and explosion-proof types).

[0035] Note: Since the rotor will function as the magnetic drive and air-moving device, special considerations for optimizing performance on both of these parameters is required.

[0036] 2. The motor/blower housing must be constructed to constrain and direct the fluid flow paths as required.

[0037]FIG. 8 illustrates a sectional view of an integrated motor/blower comprising a magnetic rotor/impeller 5, stator 13 and housing 11.

[0038] The rotor/impeller is comprised of a rotor disk 5 installed perpendicular to a stationary shaft 7 and having circumferentially arrayed impeller blades and magnetic poles shaped as impeller blades 2 and 3. The magnetic blade poles 2 and 3 on each side of rotor/impeller 5 have opposite magnetic polarities.

[0039] The stator is comprised of two parallel circuit boards 13 each having circumferentially arrayed coil windings 1 and 4. Each of the coil windings on the two circuit boards share a common axis 15 that is parallel to the rotor/impellers stationary shaft 7. The opposing stator coil windings, on the two circuit boards, have opposite magnetic polarities with respect to one another.

[0040]FIG. 9 illustrates a sectional viewpoint B of the motor/blower in FIG. 8. The coil windings 4 are aligned in a radial direction around the shaft 7 and at least partially align in a radial direction with the rotor/impeller magnets 12. This alignment allows for magnetic interaction between the rotor/impeller poles 2, 3 and the stator coil windings 1, 4 respectively.

[0041] In FIG. 8, the motor/blower housing 11 also comprises stator boards 13 for the purpose of constraining and directing fluids. The motor housing 11 maintains alignment between rotor/impeller 5 and stator boards 13, which provides for attachment of the rotor/impeller shaft 7 and shaft support pins 14. Shaft support pins 14 hold the stationary shaft 7 to the stator boards 13. The bearings 6 outer races are attached to the rotor/impeller 5, which rotates freely around stationary shaft 7. Rotor/impeller 5 maintains gaps 9 and 10 between the stator circuit boards 13 by means of the stationary shaft 7 and spacer 8.

[0042] Motor Controller

[0043] The sensing device used to control commutation of this electric drive is a Hall switch or Hall Element. An optical device may also be used but has limitations caused by interference from ambient light sources. The Hall device is located in close proximity to the rotor and positioned in respect to the coils to achieve proper rotational direction and optimum performance from the electric drive. The electronics can be an H-Bridge Drive or Two Phase-Single Ended Drive. The single ended drive stator requires a differently constructed circuit board. This circuit board requires two groups of coils wound in the same direction and having common magnetic polarities. The individual coils of one group are series connected and adjacently spaced with the coils of the other group. One end of each group of coils is connected together and ties to either the positive or negative lead of the motor power supply. (If the single ended driver is a Low End Driver, then the connected ends of the coils tie to the positive supply; if a High End Driver then they're connected to the negative or ground supply.) The other end of each of these two groups ties to the single ended driver. Only one group of coils are energized at a time.

[0044] There are many versions of Single Ended drives with different protection schemes available, however they all perform essentially the same control function. The H-Bridge Drive has a few advantages over the Single Ended drive as can be seen in the following comparison table. Items for Comparison H-Bridge Drive Two Phase Single End Drive Stator Boards coil resistance Equals the sum of all Equals ½ the sum of all seen by Motor Controller individual stator coils individual stator coils Motor Magnetic Drive Push and Pull Either Push or Pull Operation Motor efficiency More efficient than Two Less efficient than Phase Single End Drive H-Bridge Drive Operational Duty Cycle on 100% 50% Stator Board Coils Electrical Attachment Points 2 3 to Each Stator Board Stator Board Construction Requires 1 VIA for each Requires 2 VIA'S for each Stator Coil stator Coil

[0045] Operational Description

[0046] The operation of this electric drive will be briefly describe starting with the Hall device through rotation of the rotor disk.

[0047] The Hall device supplies a change in electrical states or levels used to operate the H-Bridge controller. These states or levels change in relation to the magnetic poles and gaps of the rotor disk. If the Hall device is not sensing one of the magnetic poles, then it supplies output signal that the bridge driver uses to energize the coils. The energized coils move the magnetic pole towards alignment with the attracting coil windings on the stator. Before the rotor reaches the these coils the Hall device senses the magnetic pole and changes the output of the driver causing the rotor to be attracted to the next or adjacent set of coils. Before the magnetic pole reaches this set of attracting coils the Hall device senses the loss of the magnet pole and changes the output of the driver causing the magnetic pole to be attracted to the next set of coils. This process continues maintaining a constant motion in one direction on the rotor. 

What is claimed is:
 1. A brushless DC electric motor comprising a magnetic rotor, stator and housing; said magnetic rotor comprising a disk installed perpendicular to a shaft and having circumferentially arrayed magnetic poles; said stator comprising at least one circuit board parallel to said disk; said circuit board serves as part of said housing and having circumferentially arrayed coil windings for producing electromagnetic fields; said coil windings being aligned in a radial direction around said shaft to at least partially axially align with said magnetic poles of said disk for providing electromagnetic interaction between said magnetic poles and said coil windings to cause rotation of said magnetic rotor.
 2. The brushless DC electric motor according to claim 1, wherein said coil windings are etched in circuit boards metal layers.
 3. The brushless DC electric motor according to claim 2, wherein said coil windings are plated with a ferromagnetic coating.
 4. The brushless DC electric motor according to claim 3, wherein said ferromagnetic coating is nickel.
 5. The brushless DC electric motor according to claim 2, wherein said circuit board metal layers are copper.
 6. The brushless DC electric motor according to claim 2, wherein said stator further comprises a controlling device of a type H-bridge drive, and a single layer of coil windings located on each side of the circuit board, where each said layer comprises several pairs of coil windings and each pair is made as a spiral that extends from the center of a start coil winding to a center of an end coil winding with the same turn direction of the spiral in relation to each coils center; said layers of coil windings are the same in transparent view and shifted angularly in such a way that the center of the start coil windings from one side of the circuit board are electrically connected to the coil windings on the other side of the circuit board; an electrical circuit of said one layer of coil windings is interrupted for providing power leads to the said controlling device.
 7. The brushless DC electric motor according to claim 1, wherein said circumferentially arrayed magnetic poles are like in magnetic polarity and equal half the number of said coil windings on the circuit board.
 8. The brushless DC electric motor according to claim 7, wherein said circumferentially arrayed magnetic poles are magnetized on a ferrous material.
 9. The brushless DC electric motor according to claim 7, wherein said circumferentially arrayed magnetic poles are magnets embedded in, or attached to, a non-ferrous magnetic material.
 10. The brushless DC electric motor according to claim 1, wherein said rotor further comprising at least one ferrous metal plate parallel to the disk and said circuit board is located between said disk and said ferrous metal plate.
 11. The brushless DC electric motor according to claim 1, wherein said disk further comprising blades attached in a radial pattern around said disk.
 12. The brushless DC electric motor according to claim 11, wherein said blades are shaped for the purpose of moving fluids.
 13. The brushless DC electric motor according to claim 12, wherein at least parts of said blades are magnetized in direction parallel to the shaft. 